Many chemistry practitioners rely on visual observations to determine when chemical processes and reactions are complete. For example, one conventional technique for determining the concentration of an acid is to titrate the acid by adding a basic solution of a known concentration to the acid until the endpoint is achieved. When the acid/base solution reaches the end point (i.e., the point at which the exact amount of necessary base has been added to completely react with the acid), the color of a chemical indicator in the acid/base solution changes. The practitioner can then calculate the concentration of the acid by measuring the quantity of the base that was required to reach the end point.
One characteristic feature of the technique described above is that the chemical indicator may change color very rapidly. Accordingly, the practitioner must pay close attention to the process to determine exactly when the color change begins. Another characteristic feature is that the color change may initially be subtle, again requiring close attention on the part of the practitioner. Accordingly, a drawback with this technique is that it can be difficult to accurately and consistently determine the end point of the target chemical, particularly if the practitioner fails to observe the initial color change.
One approach to addressing the foregoing drawback is to conduct the titration process in a flat-bottomed vessel such as an Erlenmeyer flask, and place the bottom of the flask against a white background, such as a sheet of paper or paper towel. By viewing the chemical solution against a white background, the practitioner can more readily determine when the solution changes color. However, this approach can have several additional drawbacks. For example, if the practitioner uses a slightly differently colored background material for successive titrations, the practitioner may not achieve consistent or repeatable titration results. Furthermore, the practitioner may wish to move the flask to achieve an optimal viewing angle, which can be awkward if the practitioner must also move a piece of paper or paper towel held against a surface of the flask. Still further, the practitioner's view of the chemical solution in the flask may be distorted by the curvature of the flask at the juncture between the bottom of the flask and the walls of the flask, particularly when the volume of the chemical in the flask is relatively small.